Drive unit for a wind turbine

ABSTRACT

A drive unit for a wind turbine is provided: wherein the wind turbine comprises a rotor rotatably supported on a machine frame with a hub and at least one rotor blade attachable thereto, wherein the drive unit has a gear box for converting the rotational speed of the rotor according to a gear box ratio, comprising at least one ring gear, a planet carrier, at least two planet wheels, a sun wheel and a output shaft, wherein the ring gear is connectable to the rotor in a rotation-fixed manner and in effective engagement with planet wheels, planet wheels are rotatably supported on the planet carrier planet wheels cooperate with the sun wheel and the sun wheel is connected with the output shaft, wherein the drive unit has a substantially horizontal rotor shaft for rotatably supporting the rotor, wherein the rotor shaft can be directly or indirectly fixedly connected to the machine frame.

TECHNICAL FIELD

The invention relates to a drive unit for a wind turbine, wherein a rotor of the wind turbine is rotatably mounted on a machine frame. The rotor comprises a hub and at least one attachable thereto rotor blade. The drive unit comprises a gear box for converting the rotational speed of the rotor according to a desired gear box ratio. The gear box, a planetary gear box comprises at least one ring gear, a planet carrier, at least two planet wheels, a sun wheel and an output shaft. The wheels of the gear box are preferably designed as gears. The ring gear is connected with the rotor in a rotation-fixed manner and is in effective engagement with planet wheels. These are rotatably supported on the planet carrier and again cooperate with the sun wheel. Since the sun wheel is connected to an output shaft, the transmitted speed can be coupled into a working machine, such as a generator.

BACKGROUNDS

From DE 103 18 945 B3, such a gear box for a wind turbine is known. Thereby, the rotor of the wind turbine has a hub with rotor blades, which are supported on the hub rotatably around its longitudinal axis. Thereby, the angle of attack of the rotor blades in the wind flow is variable. The hub is directly connected to the rotor shaft, which is supported by means of a main bearing on a machine frame of the wind turbine. The fixed outer bearing shell of the main bearing, which is connected to the machine frame, comprises in the radial direction from outside the rotor shaft and the inner radial bearing shell arranged firmly thereon. On the rotor shaft, at the same the ring gear of the planetary gear box is arranged radially internally, whereby the planet wheels are driven.

Through this construction, it arises that the entire weight of the rotor and the forces of the wind acting thereon must be diverted via the main bearings into the machine frame. This is a very high load for the bearing. In addition, a main bearing according to the prior art shows a very large diameter. Since manufacturing tolerances for roller bearings are very small anyway and will also be even smaller if, as here, the bearing also carries a part of the gear box, thus high production costs are to be expected in the embodiment of the prior art.

SUMMARY OF INVENTION

An object of the invention is to provide a drive unit of a wind turbine, and also such a wind turbine itself, which avoids the disadvantages of the prior art. Thereby, especially an advantageous and simple support for a rotor of a wind turbine with a robust and cost-reduced drive unit should be presented.

The object is achieved with a drive unit with the features of the independent claim 1. The invention includes, inter alia, that the drive unit comprises a substantially horizontal rotor shaft for rotatably supporting the rotor. The rotor shaft here could be directly or indirectly firmly connected to the machine frame. In this way, the advantage, that the forces and loads of the rotor are introduced directly into the machine frame, and the main force flow does not take place in the vicinity of the gear box and would not lead to harmful deformations there, appears for the first time. In addition, the supporting can be achieved on a central, cone-shaped rotor shaft with smaller and cheaper bearings.

According to one embodiment, the planetary gear box is formed as single-stage. In this direct effective engagement, the gear box corresponds to a classic planet gear box. Here, the planet wheels engage directly into the sun wheel. Here, the gear box turns out to be particularly advantageous and preferably a gear box ratio of about 1 to 10 is achieved. Such a wind turbine is gladly referred to as medium-speed wind turbine.

However, it is also conceivable that more planet wheels are provided, which are connected in a rotation-fixed manner with planets that are in effective engagement with the ring gear. The planet wheels are then in indirect effective engagement with the sun wheel, but are each connected to a further planet wheel and form a planetary pair. These further planet wheels are then in effective engagement with the sun wheel. Thus, the gear box ratio of the gear box can be influenced via the diameter ratios of the planetary pairs relative to each other. When the diameter of the first planet wheels which are in engagement with the ring gear is smaller than the diameter of the further planet wheels, then the ratio of the gear box is increased in contrast to the direct gear box variant.

A non-illustrated embodiment particularizes a multi-stage planetary gear box, wherein the sun wheel of the first planetary stage drives, for example, a ring gear of the following stage.

Advantageously, the gear box comprises three or four planet wheels, because this will cause that the ring gear is better supported via the planet wheels, that is, that radial and circumferential forces are transmitted to a planet carrier. Moreover, the sun wheel and the output shaft are also supported through the planet wheels in the radial direction. To achieve an optimal gear box behavior, the ring gear, planet wheels and the sun wheel are formed as gear wheels.

A remarkable feature of this invention is that preferably exclusive and no more than one output shaft is provided, which is driven exclusively by only one sun wheel. Because then a load distribution takes place onto different planet wheels towards the sun wheel. It should be emphasized that in case of a multi-stage planet gear box, the gear box shaft between the first and the next stage is not regarded as output shaft within the meaning of the preceding disclaimer. Because then a plurality of output shafts connected in series are provided, wherein only one could be connected to, for example, a generator for producing electric current. In the case of several output shafts, disadvantageously, several generators would have to be used in parallel.

According to a preferred embodiment of the invention, the ring gear is rotatably supported on the rotor shaft. Thereby, the supporting of the ring gear is avoided through an expensive external bearing with a large diameter. Here, the supporting of the ring gear can be achieved via the bearings of the hub of the wind turbine without using a own separate bearing. This leads to a reduction of the components and thus to reduced cost.

One embodiment of the invention discloses that the ring gear is supported via its own separate bearing on the rotor shaft. Here, the gear box can have a gear box bell jar, which is rotatably supported via a bearing on the rotor shaft, on which the ring gear is arranged. The hub of the wind turbine here can have its own separate bearing for supporting on the rotor shaft. This own supporting of the hub and the gear box acts here particularly positively on the load of the gear box, since thereby relative motions of a driving hub can not be transmitted to the gear box.

According to a further embodiment of the invention, the planet carrier is arranged in the wind turbine in a rotation-fixed manner relative to the machine frame or the rotor shaft. In particular, junctures are provided on the rotor shaft for indirectly or directly, fixedly connecting to the machine frame and for transmitting forces. The number of effective junctures should be at least equal to or greater than the number of planet wheels, which are in effective engagement with the ring gear.

Furthermore, the junctures may again be connected to the planet carrier; said planet carrier is again connected to the machine frame. It is conceivable here that the planet carrier is formed as a disc, which can be screwed to the machine frame. On this disc, in the case of a planetary gear box with three planet wheels, three bearing pins for the planet wheels are either provided fixedly and integrally, or can be screwed on, for example, through anchor screws. It simplifies the production of the planet carrier immensely if this is formed in several pieces with respect to the machine frame, as a rotationally symmetric disk can be manufactured in an accurately fitting manner much easier through rotational machining processing than a bulkier and heavier machine support of the wind turbine. The rotation axis is again fixed on the planet carrier via the junctures, preferably through screws, which extend until into the machine frame. Here, the connection points grasp the planet carrier nearby the individual planet wheels.

If the producing allows, then, of course, the planet carrier can be formed integrally with the machine frame, on which the rotor shaft can be directly installed then. In this case, the bearing pins for the planet wheels are also formed integrally with the machine frame or a transition region of the rotor shaft or mounted as separate bearing pins into the machine frame, into the rotor shaft or into both.

It is also conceivable—but not necessarily—that the planet wheels are supported in the transition region of the rotor shaft towards the junctures, which means that the planet carrier is formed directly with the rotor shaft, preferably as an integral component.

Since the gear box requires oil lubrication, an embodiment shows that sealing means for sealing the gear box are effectively provided between the ring gear or the gear box bell jar and the planet carrier or the machine frame. Depending on the characteristics of the invention, the sealing means are effectively arranged on the components which perform a relative motion, rotation—standstill, to each other.

The invention also comprises a wind turbine with a drive unit according to the above-described embodiments. Such a wind turbine presents a machine housing mounted on a tower with the machine frame. The rotor with the hub and at least one rotor blade that can be attached thereto is rotatably supported on the machine frame. This wind turbine shows obvious advantages in terms of reduced complexity, cost, and increased life span relative to other wind turbines according to the prior art.

Advantageously, the wind turbine is formed in such a manner that an axial offset exists between the sun wheel and a bearing of the output shaft of the gear box. Thus, in cooperation with the flexibility of the output shaft, a radial clearance of the sun wheel is achieved according to the guide of the sun wheel by planet wheels to prevent excessive load of the gear box and the bearing.

As described above, according to an embodiment, the ring gear is supported on the rotor shaft with its own bearing via a gear box bell jar. According to a preferred embodiment it is provided to support the hub of the rotor indirectly on the rotor shaft via the gear box bell jar or via the ring gear.

However, advantageously, at least one, but preferably two separate bearings are provided for the hub to support on the rotor shaft.

In order to achieve a particularly long service life and low load of the gear box, decoupling connecting means are effectively arranged between the ring gear and the rotor, in particular between ring gear and the hub, in order to substantially prevent transmitting of axial motions, radial motions and/or bending motions of the hub to the ring gear. This decoupling protects the gear box against unwanted deformations. A distribution of load takes place through the advantageous separate supporting of ring gear and rotor: the rotor shaft carries weight, thrust-, transverse- and bending forces, wherein circumferential forces—quasi free of disturbing forces—are alone transmitted to the gear box.

Another embodiment of the invention teaches to provide on the rotor shaft a transmitting device for transmitting electrical energy between components rotating relatively to each other, in particular a slip ring device. Here, passing through the rotor shaft, a power supply is achieved with the power grid of the machine housing, for example via cable, in order to drive the electrical components in the hub, such as the motors for the blades adjusting. Thereby, a transfer of control signals can also be realized.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details of the invention will become apparent from the drawings on the basis of the description.

In the drawings

FIG. 1 shows an exemplary wind turbine,

FIG. 2 shows a longitudinal section through a wind turbine with a first embodiment of drive unit according to the invention,

FIG. 3 shows a cross section through the drive unit according to FIG. 2, 3 or 4,

FIG. 4 shows a wind turbine according to FIG. 2 with a second embodiment of a drive unit,

FIG. 5 shows a wind turbine according to FIG. 2 with a third embodiment of a drive unit,

FIG. 6 is a schematic diagram of a wind turbine with a fourth embodiment of the drive unit.

PREFERRED EMBODIMENTS

To make the context of the invention clearly, in FIG. 1 an exemplary wind turbine 1 is shown. This comprises a tower 2, a machine housing 3 and a rotor 7, wherein the machine housing 3 is supported rotatably on the tower 2 around a substantially vertical axis 4 by means of an azimuth bearing 5 in order to allow wind tracking. The rotor 7 is arranged on the machine housing 3, which comprises a hub 8, on which again preferably three rotor blades 9 are arranged. The rotor 7 is supported on the machine frame 6 via the drive unit 10 according to present invention and drives a generator 32 for producing electric current.

FIG. 2 shows the first embodiment of the drive unit 10 of the wind turbine 1. However, the details described below substantially refer to other embodiments. FIG. 2 shows primarily the machine housing 3, the drive unit 10 and the rotor 7. A machine frame 6 in the machine housing 3 is connected with the azimuth bearing 5, whereby the machine housing 3 is supported on the tower 2 of the wind turbine 1 rotatably around the axis 4 by means of the azimuth bearing 5. The preferably cone-shaped rotor shaft 11 is arranged in a rotation-fixed manner again on the machine frame 6 via junctures 15, wherein the rotor shaft 11 and the junctures 15 can be formed integrally. The hub 8 is rotatably supported on the rotor shaft 11, wherein this extends substantially horizontally. The hub 8 comprises an access opening 39 to allow an access for machinists into the hub 8 in case of maintenance. In order to orientate, an axial direction 12, a radial direction 13 and a circumferential direction 14 are defined with respect to this axis of rotation or the rotor shaft 11 of the rotor 7, which also applies to the following embodiments.

The hub 8 of the rotor 7 is connected in a rotation-fixed way to a ring gear 20 of a gear box 18 via elastic connecting means 17 via a gear box bell jar 19, wherein the gear box bell jar 19 and the ring gear 20 may be formed as one piece. Thus, the ring gear 20 takes the same rotation as the rotor 7. The rotational motions of the ring gear 20 is further transmitted to planet wheels 23, which are rotatably supported in a planet carrier 26 by means of bearing pins 25. The planet carrier 26 is provided in a rotation-fixed manner relative to the machine frame 6, in particular, the planet carrier 26 can be formed, according to FIG. 2, by a transition region 16 of the rotor shaft 11 to the junctures 15, or according to FIG. 4, via a separate planet carrier 47, or according to FIG. 5, directly from the machine frame 6. To some extent, the ring gear 20 is supported via the planet wheels 23 on the machine frame 6 or on the rotor shaft 11.

In present embodiments, three planet wheels 23 are provided, wherein this is not to act in a limiting way on the invention, but two, four, five or six planet wheels are also conceivable.

The ring gear 20 is connected to a housing 22 and a gear box bell jar 19 and forms a structural unit, which is connected to the hub 8 in a rotation-fixed manner via the connecting means 17 and consequently rotates together with the rotor 7. The initial rotation of the rotor 7 is transmitted via the ring gear 20 to the planet wheels 23 and—now at a higher rotational speed—transmitted to the sun wheel 29 in the center of the gear box 18. The sun wheel 29 is connected to an output shaft 31, which further transmits the rotation at a medium-fast, increased rotational speed to a generator 32 for producing electric current. The output shaft 31 is preferably provided with a braking disc 33, wherein a non-illustrated brake device can act on it for the mechanical braking of the drive train or of the drive device 10.

The output shaft 31 is either supported directly in the machine frame 6 and/or on the machine frame 6 via a common bearing 34 with the generator 32. The common bearing 34 of generator 32 and output shaft 31 is particularly simple and advantageous in terms of manufacturing and assembly of the wind turbine 1. This combined bearing 34 here can be used particularly well, since the three or more planet wheels 23 present also an effective supporting in the radial direction 13, whereby an another bearing nearby the sun wheel 29 may be abandoned. Between the bearing 34 of the output shaft 31 and the sun wheel 29, an axial offset Lx exists. Because of the fact that the output shaft 31 can deform slightly elastically, the sun wheel 29 is capable of performing a radial motion between the planet wheels 23 to some conditional extent and thus to ensure a similar load situation between the planet wheels 23. This reduces the wear of the planet wheels 23 and the sun wheel 29.

FIG. 3 shows a simplified section through the gear box 18 along the line A-A of according to FIG. 4. Since the present embodiments do not differ significantly in terms of the gear box 18, this also applies to the other embodiments. In FIG. 3, adjacent to the rudimentarily illustrated rotor blades 9, the housing 22 of the ring gear 20 can be seen, wherein the ring gear 20 is only shown on the basis of the center circle of the dash-dot line representing the tooth 21. The housing may be formed integrally with the ring gear. It is also conceivable, however, to shrink the ring gear 20 as a full-ring into the housing 22 or bring it into the housing 22 in segments via form- or friction-fit.

Further radially inwards, a dotted line 16 can be seen, which represents the transition region 16 between the rotor shaft 10 and the three junctures 15. This transition region 16 is used in the embodiment shown in FIG. 2 as a receiver for the bearing pin 25 and, consequently, as a planet carrier 26. The rotor shaft 10 for supporting the hub 8 and the ring gear 20, the transition region 16 formed as a planet carrier 26, and the junctures 15 for attaching onto the machine frame 6 then form an integral structural unit, which can be produced, for example, as a cast.

However, it may also be advantageous in terms of assembly and manufacturing, to produce this structural unit from several parts, for example according to FIG. 4.

The planet wheels 23 engages with the tooth 21 of the ring gear 20 and the tooth 30 of the sun wheel 29, wherein the teeth 24 of the planet wheels 23 is shown as a dash-dot line 24 (center circle).

Radially further inward, a further dotted line 44 can be recognized, which represents the rotor shaft 11 and the bearing surface 44 on the rotor shaft 11 of the bearing 36, 46 of the gear box bell jar 19.

The above embodiments apply generally to all wind turbines in accordance with FIGS. 2, 4 and 5. In following, the main differences of the present embodiments are given—these differences concern the supporting of the hub on the rotor shaft, the formation of the planet carrier and the rotary connection between the ring gear and the hub. The characteristic differences disclosed in following embodiments are not tied to the respective embodiment and are not to act in a limiting way on the invention, but the characteristics of the different embodiments could be combined with each other. In particular, the different forms of direct or indirect supporting of the hub on the rotor shaft or the different coupling types of rotary connection between the hub and ring gear can be combined with the different characteristics of the planet carrier.

In FIG. 2, the hub 8 is supported via a direct bearing 35 at the tip 37 of the rotor shaft 10 and indirectly via a bearing 36 of the gear box bell jar 19 of the ring gear 20 on the rotor shaft 10. Since the hub 8 can perform a motion 38 together with the tip 37 due to bending, however this shall not be transmitted to the ring gear 20, decoupling and/or damping connecting means 17 are provided between the hub 8 and the gear box bell jar 19. These enable that a substantially rotation-fixed connection is established between hub 8 and gear box bell jar 19 or ring gear 20, however no significant axial motions can be transmitted. Such motions would result in that the engagement of the ring gear 20 and the planet wheels 23 would be very irregular and variable, whereby it would come to a very high wear of the teeth or the destruction. The embodiment in FIG. 2 requires that the connecting means 17, the hub 8 and the gear box bell jar 19 do not decouple with respect to the radial motions, since the supporting of the hub 8 is achieved via the bearing 36 of the gear box bell jar 19 or the ring gear 20 in a combined manner, wherein a radial support is indispensable. The connecting means 17 may also absorb torsional vibrations.

The connecting means 17 according to FIG. 2 may be implemented, for example, as a bush, wherein an elastomeric body 40 is arranged in or on the hub 8, or in the gear box bell jar 19 (not shown). The elastomeric body 40 again accommodates a bolt 41, which is fixedly arranged in the gear box bell jar 19 or in the hub (not shown). Here, the bush is formed in such a manner that the bolt 41 is relatively flexibly supported in the axial direction 12, but not in the radial direction 13. Preferably, three or more such connecting means 17 are provided between the hub 8 and gear box bell jar 19.

Sealing means 27, which seal the gear box 18 relative to the machine frame 6, are provided on the housing 22 of the gear box 18.

With reference to FIG. 4, a further embodiment of the invention is introduced, wherein the hub 8 is supported on the rotor shaft 10 by means of two direct, separate bearings 42, 45. Advantageously, one of the bearings 42, 45 is designed as a fixed bearing and one as floating bearing. The gear box bell jar 19 and the ring gear 20 have their own independent bearing 46 for supporting on the rotor shaft 10. Connecting means 47, which decouple with respect to axial and radial motions and can also be designed as a bush, are now arranged between the hub 8 and the ring gear 20. This brings the great advantage that now the ring gear 20 and the hub 8 are substantially decoupled in the radial direction 13 and axial direction 12 and no interfering motions 38 can be transmitted from the rotor 7 to the gear box 18. According to FIG. 4, the decoupling means 47 is formed in such a manner that the hub 8 and the gear box bell jar 19 have areas which overlap in the axial direction 12, but are offset in the circumferential direction 14. Between these areas of the hub 8 and the gear box bell jar 19, elastomeric bodies 48 are provided, which although transmit tangential forces from the hub 8 to the gear box bell jar 19, and vice versa, but allow to some extent the axial and radial displacement of hub 8 and the gear box bell jar 19 relative to each other. Thus, an advantageous and effective gear box of the rotational motion is achieved, without transmitting the harmful radial and axial motions 38.

To achieve a low-cost manufacturing of individual components, an independent expression of the planet carrier 49 is proposed, as shown in FIG. 4. This consists substantially of a disc 50, which again carries the bearing pin 51 of the planet wheels 23. The disc 50 can be produced very accurately and economically through turning and/or milling processes and thus mounted with screw connections on the machine frame 6. As the disc 50 of the planet carrier 23 accommodates also the junctures 15 of the rotor shaft 11, mainly by screw connections, the disc 50 determines the axial spacing of the individual gears 23 of the gear box 18, which are highly relevant to the functioning and service life of the gear box 18.

Sealing means 52 are arranged between the disk 50 of the planet carrier 49 and the housing 22 of the ring gear 20.

Furthermore, FIG. 5 shows that however it is conceivable in all other embodiments to provide a transmitting device 53 on the rotor shaft 11 for transmitting electrical energy between the rotor shaft 11 and the hub 8 which rotates relative to the rotor shaft. This device formed as a slip ring device comprises one or more collectors 54 rotating with the hub 8 and the slip ring 55 connected with the hub 8. The multi-pole slip-ring 55 is connected by cable to the power grid of the machine housing and connected to the controlling device of the wind turbine 1 for transmitting control signals.

The embodiment shown in FIG. 5 corresponds to the foregoing in many respects, wherein the rotor shaft 11 is formed as a stub axle 56 without tip. Instead, the rotor 7 is supported on the stub axle 56 over the hub 8 via a so-called torque bearing 43. This leads to a reduction in weight and meanwhile enlarges the space inside the hub 8, in order to accommodate here drive components for adjusting the angle of attack of the rotor blades 9.

The planet carrier 26 here is formed directly by the machine frame 6, wherein the bearing pins 25 are arranged in the material of the machine frame 6.

FIG. 6 schematically illustrates a more detailed embodiment of the gear box 18 in accordance with FIG. 2, 4 or 5. It is here essential that the planet wheels 23 do not directly act on the sun wheel 29, but each planet wheel 23 in effective engagement with ring gear 20 is assigned with a further planet wheel 57. Thus, the ring gear 20 drives a planetary pair 58, wherein the further planet wheel 57 acts on the sun wheel 29 respectively. So the gear box ratio can be influenced by the proportions of planetary pairs 58 relative to each other.

List of reference signs 1 drive shaft 2 tower 3 machine housing 4 axis 5 azimuth bearing 6 machine frame 7 rotor 8 hub 9 rotor blades 10 drive unit 11 rotor shaft 12 axial direction 13 radial direction 14 circumferential direction 15 junctures 16 transition region 17 connecting means 18 gear box 19 gear box bell jar 20 ring gear 21 teeth (ring gear) 22 housing 23 planet wheels 24 teeth (planet wheel) 25 bearing pins 26 planetary carrier 27 sealing means 29 sun wheel 30 teeth (sun wheel) 31 output shaft 32 generator 33 braking disc 34 bearing (generator) 35 bearing (tip) 36 bearing (combined bearing) 37 tip 38 motion 39 accessing opening 40 elastomeric body 41 bolts 42 bearing (tip) 43 torque bearing 44 bearing surface 45 bearing (hub) 46 bearing (gear box bell jar) 47 connecting means 48 elastomeric body 49 planetary carrier 50 disc 51 bearing pins 52 sealant 53 transmitting device 54 collectors 55 slip ring 56 stub axle 57 planet wheel 58 planetary pair Lx axial offset 

1. A drive unit for a wind turbine, wherein the wind turbine comprises a rotor rotatably supported on a machine frame with a hub and at least one rotor blade attachable thereto, wherein the drive unit has a gear box for converting the rotational speed of the rotor according to a gear box ratio, comprising at least one ring gear, a planet carrier, at least two planet wheels, a sun wheel and a output shaft, wherein the ring gear is connectable to the rotor in a rotation-fixed manner and in effective engagement with planet wheels, planet wheels are rotatably supported on the planet carrier planet wheels cooperate with the sun wheel and the sun wheel is connected with the output shaft, wherein the drive unit has a substantially horizontal rotor shaft for rotatably supporting the rotor, wherein the rotor shaft can be directly or indirectly fixedly connected to the machine frame.
 2. The drive unit according to claim 1, wherein the planet wheels directly engage into the sun wheel.
 3. The drive unit according to claim 1, wherein further planet wheels are provided, which are connected in a rotation-fixed manner to the planet wheels which are in effective engagement with the ring gear, wherein these further planet wheels are in effective engagement with the sun wheel.
 4. The drive unit according to claim 1, wherein the ring gear is directly or indirectly rotatably supported on the rotor shaft.
 5. The drive unit according to claim 5, wherein the gear box has a gear box bell jar which is rotatably supported on the rotor shaft via a bearing, wherein the ring gear is arranged on the gear box bell jar.
 6. The drive unit according to claim 1, wherein the planet carrier is fixedly connected to the machine frame.
 7. The drive unit according to claim 1, wherein junctures are provided on the rotor shaft for indirect or direct connection with the machine frame, wherein the number of effective junctures is at least equal to or greater than the number of planet wheels which are in effective engagement with the ring gear.
 8. The drive unit according to claim 8, wherein the junctures are connected with the planet carrier, which is connectable to the machine frame.
 9. The drive unit according to claim 1, wherein sealing means for sealing the gear box are effectively provided between the ring gear, the gear box bell jar or housing and the planet carrier or the machine frame.
 10. The wind turbine comprising a tower, a machine housing rotatably supported thereon with a machine frame, one rotor rotatably supported on the machine frame with a hub and at least one rotor blade attachable thereto, wherein a drive unit according to claim 1, which is arranged on the machine frame.
 11. The wind turbine according to claim, wherein the output shaft is rotatably supported in the machine frame by means of a bearing in such a way that an axial offset (Lx) is present between the sun wheel and the bearing, which enables a radial clearance of the sun wheel in cooperation with the stiffness of the output shaft according to the guiding of the sun wheel through planet wheels in order to prevent excessive loading of the gear box.
 12. The wind turbine according to claim 11, wherein the hub of the rotor is indirectly supported on the rotor shaft via the gear box bell jar.
 13. The wind turbine according to claim 11, wherein the hub is directly supported rotatably on the rotor shaft via at least one further bearing.
 14. The wind turbine according to claim 1, wherein decoupling connecting means are effectively arranged between the ring gear and the rotor to substantially prevent transmitting of axial motions, radial motions and/or bending motions of the hub to the ring gear.
 15. The wind turbine according to claim 1, wherein on the rotor shaft a transmitting device for transmitting electrical energy between to each other relatively rotating components, in particular a slip-ring device is provided, which is connected through the rotor shaft to a power supply and/or control unit of the wind turbine. 